awschucks

Hi,
In a past life, I worked on contact reliability issues with Bell Labs. I was working on making contacts more reliable for central station switching applications. I also worked as a counsultant on the GM check engne light issue in the late 80's.

I'm reading that there is a potential lethal problem with a connector under the steering wheel. The Steering WPS (wheel position sensor) has a resistance value that is monitored by the active handling computer. The AHC will apply the brakes on one or more wheels to get the car to turn if you turn the steering wheel and the car does not follow your original steering wheel turn. What this means is you cannot do a doughnut or if you go into a turn too fast the car will follow your steering commands and not spin out.

Now if the connector under the dash has an intermittent connection, it can send a fake message to the AHC that you have turned the wheel. (without looking up the values, I would guess that this will send a right turn indication to the AHC). This is the stage for a real problem.

Now what to do about this?

It's a long story, but many connectors fail on the first use, much less when they are getting pulled back and forth with the steering column making the 'fretting' issue a real problem. Actually, fretting usually describes micro movements. The problem here is closer to wearing. Anyway, for a contact to be reliable, it must have what Bell Labs calls an gas tight connection.


This can mean a pure gold to pure gold contact that assures no corrosion, or a high pressure area that has a gas tight connection. It may also mean you try to take cheap contacts and keep air out other ways.


The best fix, short of soldering the wires, is to use a liberal coating of white lube on the contacts. At first glance, this might sound crazy, but the contacts will poke thru the lube to make a good contact and the white lube keeps air out to help keep the contact good. If you have worn thru the contact plating, you will have dissimilar metals eating away at each other and contact reliability issues. Keeping air out helps keeps contacts from corroding, even if you have plating problems. (Almost all cheap contacts have plating problems) Low current applications like this have many more reliability problems than higher current connections.

I had two patents relating to this issue and from extensive testing can assure you, lube helps. You might see some car manufactures using white lube in all of their connectors that might be exposed to salt and water. The lube that we sold to Bell Labs was $1600 a quart for central station applications, but white lube is a good alternative



So now lets assume that you have had a DIC mesaage to service the active handling. You might want to have checked your life insurance at this time.

If the connector under the steering wheel has a bad connection it will send the fake signal to the Acive Handling computer and the active handling system will apply the brakes to get the car to turn, as the computer thinks you have turned the steering wheel. Let's say you are tooling along a two lane road at 80 mph and a small bump causes the connector to send a hard right turn signal to the AHC and the computer will apply hard right rear wheel brakes. Off you go to the right. YIKES.

I believe this is happening a lot more than people realize. Many people are being blamed for not being able to drive a high performance car, but as you read other members description of these events, it seems like the car may be responsible for some of the problems.

I am repairing a 2007 C6. The owner says the car just spun out on its own and went into the ditch rolling three times. Can you believe, no one was hurt and the frame was not damaged. I did retrieve active handling error codes and I would be willing to bet this caused the car to spin out.


Dave

Miaugi

0Randy@DRM

I know of 3 c5s that are no longer with us because of these issues. The reports from the drivers, I was going just fine, and the car went to the right hard and fast. "Like the brakes got applied". 2 out of the 3 are good drivers and know what they are doing.

Randy

AORoads

that's a pretty important write up. hmmm. good info. thank you.

1.8t

Looks like I will be turning the system off everytime I fire up the car from now on.

Kent1999

I guess it's *possible*, but ....?

I had the AH steering sensor in my C5 fail, and I also had the 'loose AH steering sensor connector' problem on my C6 for the first 3,000 miles I owned it. I guess I was lucky on both counts, as neither car ever spun out or acted like it was going to. Not even a twitch, just the annoying "Service Active Handling" error about 5-10 minutes after starting out.

On another vehicle, I had a rear wheel lock up going down the road at 60mph (manual, non-ABS brakes, brake shoe came loose and wedged), but all it did was skid and slow me down, and I easily corrected with a little steering and pulled off to the side -- given that, I don't know if one wheel locking would immediately throw you in the ditch... would it? I mean, all three other wheels are still full traction, tracking and rolling, and I don't think AH allows a wheel to go from 60mph to full locked braking, just because you turned the wheel sharply (or it thinks you did), does it? (maybe it does, but it seems unlikely)

Again, I'm not saying it *cannot* happen, just that I don't know:
A) how likely a failed sensor is to lock (or near-lock) a wheel, and
B) if it would lock, how likely is that to cause a sudden, non-correctable vehicle over-rotation.

Clearly, GM has connector reliability issues as the OP stated (and many of us have experienced first-hand), and it's also clear that a near-locked wheel could *contribute* to an unintended off-road event, but could it be the sole cause with enough probability to warrant losing all the other benefits of the AH system?

Good discussion thread, and it will be interesting to read. Thanks to Dave for providing a lot of good info on connector reliability. It's people like that who take the time to share their expertise that makes this forum so great.

Rob 99

Does this apply to C5's as well as C6's(i own both)?
Would the bad (or worn out plated) connection send a continious code to the DIC?
What is the cost to replace this part preventivly, not sure i would want to gamble on this
Thanks for the very informative warning.

awschucks

Hi,

In response to one discussion item above, locking up a wheel is a lot different than the ABS system applying the brakes to the right rear. A 'locked' up wheel has a very low coficient of friction making it fairly easy to steer the car with one wheel locked. In the case of ABS applied brakes you will get a car that is almost impossible to control with the other wheels as they all have about the same friction. As an example, ABS systems can stop a car faster than most drivers. Computer brakes keep the wheel turning just above the point where it will skid.

Second response: Both C5 and C6 share the some design.

The most likely cause of a problem would be an intermittent signal to the AHC based on a bump or other vibration. You should see a warning on the DIC about servicing the Active Handling Computer if you have a problem with this connector.

I have been reading other forum discussions about seeing this warning and they are suggesting the solution is wiggling the connector. This is not going to fix the problem and may be creating a potential problem with the handling of the car that can cause the brakes to self apply on selected wheels.

If you see the warning and have the connector serviced, I'm suggesting that you or the tech use white lithium lube on the connector. You should also make a determined effort to keep the connector from flexing when the steering wheel is moved in and out.

You might try to replace the connector, but that brings up a full can of worms. Should I use the existing connector design or use something better? As I said earlier, solder is the best, but there are better connectors that could be used if you want to fix this once and for all.

0Randy@DRM

The Yaw sensor was to blame on all the C5's that I know of. They all had a "mastic" problem.

Randy

Zig

hhmmm.....good info. and thanks for sharing.

yes, i agree, the 'drivers aids' have the potential to cause catastrophe and a 'intermittent fault' would only compound the potential.

question: what would a 'gm tech' do if one applied some 'white grease' to the connectors and it did not resolve the issue. i mean, what wold they do if i applied some 'grease' to the connectors (i drive with all-off but my wife does not) and it didn't fix the 'service' messages causing me to take it in for repair. would they balk at it because i added the grease or attempted to resolve the issue myself?

awschucks

Hi,
I can't speak for what a GM tech might do, but I know what I will do if I find the problem on a car that I am going to be driving. I would replace the connector with something better.

P.S. Ford does use the lube on most of their connectors. Many other car folks use it as well.

If I was a GM tech, it would probably replace the connector, but realize the connector may be the problem. The connector may have bad plating that is the root cause of the problem. Again, in my experience, many connectors fail on the initial insertion. This is a real problem where you are using the connector in low current applications, like monitoring a pot. like the WPS.

http://www.digikey.com/ has thousands of connectors that may offer better realiability.

If you were to completely eliminate the suspect connector with a hard wired splice, you would completly eliminate the connector problem. If at some time you needed to replace the steering wheel position sensor, you would have to hard wire the new one in. Big deal.


Dave

CMY SIX

I agree with #8 but in this day and age a flat tire cause's a multiple rollover accident

PowerLabs

Dave,

I think your doomsday scenario might be grossly oversimplifying how Active Handling works.
It is a lot more than just a steering angle sensor. For starters, before it can take any action, the system relies on not one, but 4 sensors to determine what the car is doing:
- Steering wheel position sensor (the one you are worried about)
- "G" sensor (detects cornering forces)
- Yaw sensor (detects pitching motion, to determine if the car is undergoing oversteer)
- Abs wheel sensors (detect wheel motion in relation to the other wheels)
If one sensor is in disagreement with the others (say, your plug has a bad contact), you will see a "Service Active Handling" message on your HUD and the system will be disabled.
And you won't die.
Then you look at how the system works. Once it has detected and confirmed through its various sensors that the vehicle is not following the path intended by the steering wheel it will apply SOME braking pressure to one or two wheels to produce SOME tuning moment in the car. It by no means can take over the vehicle: you can, and I have, on several occasions, spun the car, slid, performed donuts, etc all with active handling on. The system will try and prevent it, but it is very much limited by the laws of physics and ultimately anything you do with your steering wheel is going to produce a lot more force than some braking force on one or two wheels. Try it at an autocross some time, just make sure you have room to go when your car does spin out.
Its sad but some people here (not referring to you!) think that AH controls their car. I have read not one but TWO threads where someone crashed their vehicle and they, or another poster, actually wondered how it was possible to crash a corvette if these cars have active handling . Seriously! As a Mechanical Engineer I marvel at what these systems can do, but I am also very aware of their very real limitations. We all should be.

I almost made a comment about how this sounds like "fear of technology and innovation", but I know you are much smarter than that.

BTW here is a nice simple explanation of active handling: http://www.corvetteactioncenter.com/...1061997_4.html

jimman

awschucks

Fact: A number of experienced drivers are loosing control of their cars and ending up in the ditch.

Fact: The cars seem to spin out to the right.

I'm writing the above to offer an explanation of how this might happen.

Fromt the article on how active handling works:

Faced with that scenario, many drivers may turn the wheel abruptly to the left to avoid the pothole. That input, combined with the reduced traction available, could exceed the limits of traction available to the front tires, and a condition called "understeer" could make itself apparent. In an understeer situation the car tends to plow straight ahead -- not at all what the driver may want it to do.

In this scenario, Active Handling will work to help correct the car's understeering behavior by automatically applying the left side front brake, helping to "pull" the car into the left turn.



The handling computer monitors the steering wheel position and if you turn the wheel the above situation will occur.

What I am saying is: if the connector produces a fake right steering wheel turn and you are traveling at high speed, a brake is going to come on. It's one thing to be on a skid pan and doing turns, it's another to be crusing down a highway at 80 mph lost in the experience and suddenly the car tries to turn right on it's own. I would suggest that even the best drivers among us would not be prepared to suddenly have the car trying to trun right.

I have reviewed the circiuts in the steering wheel position sensor and it is not just a simple pot, but has a 5 volt reference voltage and two pots that produce two signals. The net of this is it would be very unlikely for all of our cars to be going to the right. I would suggest if you have the error message to service the active handling, to not just wiggle the connector, but replace it.

Not trying to make a doomsday, just trying to tell the people that are wiggling the bad connector, that other options are better.

P.S. as the last contributor points out, acitive handling will not be able to help if you come into a corner at 100 mph and suddenly try to turn into an alley. The good news is that the car will follow your steering wheel inputs up until the wheels all start skidding and after that point, your car is responding to Newton's laws of physics. You can turn that wheel all that you want, but the active handling can do nothing if you take a corner at twice the speed that you should.

When I was teaching my kids to drive, we would go onto a lake and practice driving on pure ice. It's a wonderful way to learn how the coefficient of friction is different for a rolling tire and a skidding tire. It is really cool to see just how fast you can drive before you loose a car in a turn. Many drivers have probably never experienced what happens when you take a corner too fast or try to stop too fast. If you turn off all of the ABS and active handling helpers or take your 1955 Buick out on a lake, it's a real learning experience. Even more fun if you have a Corvair and take it around a corner too fast. Quick lessons in oversteer with the Corvair and understeer with the Buick.

Hmmm, maybe I have found a new way to teach high performance driving by taking people out on our lakes and have them try to do an autocross at something over 10 mph. It's really fun to blast around at 15 mph on a sheet of ice and learn how to countersteer and correct for driving mistakes at low speeds and with nothing to hit. I remember my wife trying to stop and forgetting to push the clutch in at about 20 mph. She killed the engine in a front wheel drive car and took out a couple of cones with lots of wheel turning and some screaming. Of course, the front wheels were not turning and she had no control of the car. She learned to push in the clutch on ice and brake carefully. Even though the car had ABS, because the engine was not running, she had no control of the car. Fun was had by all.

Dave

PowerLabs

Fact#3: I have never, in my entire life, met a man who admitted to being at fault for crashing his car. NEVER! Search the forums for "crash" or "crashed". You will find nothing but "the road was wet", "I hit a patch of water/ice/oil/sand/dirt/whatever", "someone cut me off", "the car wasn't right", "my tires were bald", "there was something wrong with the road", etc etc etc. Where are all the drunk drivers, the people who drive too fast, take corners too fast, don't know what they are doing, get in over their heads, etc etc... Where are the people who think that, just because they bought a powerful car, have now all of a sudden become race car drivers and feel like the street is their racetrack?
Just a thought


Aha, again you are oversimplifying things See, I thought of that before I posted, so I went and checked out what GM uses for a steering wheel position sensor. GM (and, I presume, other manufacturers as well) uses optical encoders. We had a class on those in Engineering school, so, while I don't claim to be an expert, I do know the principle behind how they work; the encoder runs a light beam through a slotted wheel and that produces light pulses; by counting the pulses it can figure out how many degrees the wheel has been turned. Thus the sensor outputs a square wave, something that can not be easily corrupted by a change in the resistivity of the connector.


I agree. I went to school in Upper Peninsula Michigan and built an engine-swapped sub 2800lbs Subaru 2.5RS that put down 320horses to the ground on all 4 wheels. The engine was pushing 22psi boost and redlined at 8200RPM. In winter I would swap out my 17" maximum performance tires and slap on 16 inch 205 width Blizzak Revo 1 tires; the ones with microscopic silicon carbine granules imbedded in the rubber for traction. It was AMAZING. Raced it in Michigan, Wisconsin and Minessota, got a couple trophies for it. The Wisconsin and MN races were on bare ice frozen lakes, and even with the snow tires the car would slide continuously everywhere, in any gear. Those were some of the best times I've ever had in a car. No active handling here; just all wheel drive and the power to spin those tires at any speed.

John Shiels

Dam I'm selling my two cars and getting a 63 I would hate to make a right turn at Pocono into the so called soft wall.

gfacter

This is interesting, I put my car into a guard rail in November, minor paint work needed, but a PITA still

Anyway I was out on a mountain road in 3rd gear going maybe 50 MPH, was just cruising at low RPM and must have just hit the max torque and spun the rears a bit, next thing I know I am scraping the guard rail...

I usually put the car in Comp mode when in the twisties, that day all the nannies were on, when the wheels started to spin, (the car rotated to the left) the TC killed the power and I seemed just turn right in the rail. I think perhaps this was mostly due to lost foward momemtum, but this thread has me thinking a little.

FYI I have more than 60+ car track days (HPDE) and found the Active handling annoying and turned it off on the race track.

Also I have never had a single vehicle accident in a car on the street before.

robvuk

Children have been known to get hurt while operating power windows. People have been known to be trapped in cars on fire by their seat belts. Airbags have been known to brake arms or actually kill some occupants. ABS has been known to cause accidents on deep gravel. Power steering pump failures have caused people to lose control.

AH is a safety feature. There's no doubt that it will at some point be the RARE cause or participant of an accident if it hasn't already been the culprit in SOME of the above mentioned cases. People aren't going to stop using parachutes because on rare occasions they don't open.

Kent1999

Did you get a "SERVICE ACTIVE HANDLING" error? Given how the steering sensor works (thanks PowerLabs), a erroneous and spontaneous "hard right turn" signal from the sensor seems extremely unlikely.

We have, so far:
A) events where reportedly experienced drivers lose control of a lightweight, high-horsepower vehicle.
B) incidents of active handling components failing.

What we are missing is the root cause analysis or 'smoking gun' linking A and B. Just because "A" and "B" exist at the same time doesn't prove they are related. This does not mean that a linkage will never be established -- just that no reliable evidence of such linkage currently exists.